The invention relates to a self-adhesive coating for polypropylene foam materials, especially for postformable soundproofing moldings in motor vehicle construction. These moldings consist of pelleted matrix foams and they have the best sound absorbing qualities at the present time.
However, the resulting moldings have mechanically delicate surfaces, are easy flammable and undesirably soften when in contact with diesel fuels. These characteristics are highly undesirable.
In the present state of the art, these deficiencies have not been satisfactorily eliminated for polyolefins, especially polypropylene. Since modification of the foam composition has not produced satisfactory results, coatings containing flame-retardant additives, e.g., on the basis of chlorinated polyethylene, polyvinyl acetate, polyvinyl chloride or polyurethane, have been applied to polyolefin surfaces to protect them. None of the known materials, however, are sufficiently resistant to diesel fuel. Further, the proposed coatings have poor adhesive properties are very poor especially on polypropylene foam surfaces that are to be postformed. Pretreatment with an adhesion-mediating agent (primer) before bonding has not produced satisfactory results.
The object of the present invention is to overcome the above drawbacks of prior art techniques by use of a flame-retardant coating for polypropylene foam materials which is resistant to diesel fuel, provides protection against mechanical and chemical attack, will have better postforming qualities, and which will adhere securely to the surface of the foamed materials without the use of a primer, while maintaining the good sound proofing qualities of polypropylene foam.